The Application Of Graphene Oxide And Fluorescent Nanoparticles In The Biosensor

In recent years, biosensor, containing various fields of biology, chemistry,medicine, electronics et al, has attracted more and more attention. It is derived fromchemical sensors, which has the advantages of high selectivity, rapid analysis, highsensitivity, low cost etc. Biosensors can quickly and sensitively detect ions, smallmolecules, proteins and DNA in biological medium, and then be used for bioimaging.It has become an important research direction in the field of life science. Because ofits simple operation, low cost, fast detection speed, high sensitivity, the fluorescentbiosensors has been widely used in the field of biological analysis.With the development of medicine and scientific research, people urgently needsome low cost, high sensitivity, selectivity, non-toxic fluorescent biosensor. Amongthem, a very important research direction is to explore the use of nanomaterials influorescence biosensor. Nanomaterials refer to the functional materials that arecomposed of ultrastructure in nanoscale. Due to the characteristic structure ofnanomaterials, the nanomaterials have some special properties, such as small sizeeffect and surface effect. The use of nanomaterials will provide a new way for thedevelopment of biological sensors.In the chapter1, we described the attractive synthesis and application of grapheneand fluorescent nanoparticle in biosensor. Finally, we provided insights into utilizationof their properities for developments of novel biotechnology and the significance andcontents of this dissertation.In chapter2, we established a novel fluorescence sensing system for the detectionof biotin based on the interaction between DNA with graphene oxide and a terminalprotection of biotinylated single-stranded DNA fluorescence probe by streptavidin. Inthis system, streptavidin could bind to the biotinylated DNA that protected the DNAfrom hydrolysis by Exonuclease I. The streptavidin-DNA conjugate was then absorbed to the graphene oxide resulting in the fluorescence quenched. Upon theaddition of free biotin, it would compete with the labelled biotin for the binding sitesof streptavidin and then the Exonuclease I could digest the unbound DNA probe from3′to5′termini, releasing the fluorophore from the DNA. For the weak affinitybetween the fluorophore and GO, the fluorescence was recovered. The proposedfluorescence sensing system was applied for the determination of biotin in some realsamples with satisfactory reproducibility and accuracy. This work could provide acommon platform for detecting small biomolecules based on protein-small moleculeligand binding.In chapter3, we propose a novel approach for turn-on fluorescence sensingdetermination of glucose. By taking advantage of the super fluorescence quenchingefficiency of GO and specific catalysis of glucose oxidase, the sensitivity andselectivity of this GO-DNA sensing platform are highly satisfying. Hydrogenperoxide (H2O2) is produced from glucose oxidase catalysis oxidation of glucose. Dueto the present of ferrous iron (Fe2+) and H2O2, hydroxyl radical (OH) is generatedthrough the Fenton reaction and attacks the FAM-labeled long ssDNA to cause anirreversible cleavage by the oxidative effect of OH, producing the FAM-linked DNAfragment. Due to the weak interaction between GO and short FAM-linked DNAfragment, a restoration of fluorescence can be recorded with the addition of glucose.Finally, the GO-DNA sensing platform is successfully applied to detect glucose inhuman serum.In chapter4, Mn:ZnSe/ZnS core/shell doped quantum dots (d-dots) with3-mercaptopropionic acid (MPA) as the stabilizer are successfully synthesizedthrough a simple one-pot synthesis procedure in aqueous solution. We optimize thevarious synthesis conditions. The photostability and chemical stability have beenstudied and the resulting core/shell quantum dots are used as fluorescent label inhuman osteoblast-like HepG2cell imaging.In chapter5, we established a simple, sensitive, low cost and label-free strategy to detect the3′-5′exonuclease activity of exonuclease III (Exo III) using double-strandDNA (dsDNA)-templated copper nanoparticles as fluorescent probe. Upon theaddition of Exo III, the Exo III can digest dsDNA probe. With the decrease of dsDNAtemplates, the formation of fluorescent Cu NPs would be inhibit. Thus, thefluorescence intensity of dsDNA-Cu NPs would decrease. Compared to the previousreports, this strategy does not need any complex DNA sequence design, fluorescencedye label, modified DNA and sophisticated experimental techniques. This strategyproposes a new method to detect3`-5`exonuclease activities.